Cystic Fibrosis (CF), an autosomal recessive disease, affects approximately 1:1600 of the white population. The risk of carrying a single gene for cystic fibrosis is high, approximately 1 in 20. Pleiotropic expression of the homozygous genotype may include defects in sodium transport, pulmonary and pancreatic insufficiency and the presence of abnormal, viscous mucus. The basic defect remains unknonw. The goal of this proposal is to search fo a DNA polymorphism that segregates with the defective gene responsible for cystic fibrosis. Restriction fragment length polymorphisms (RFLPs) can be detected by probing endonuclease digests of human lymphocyte DNA, separated electrophoretically according to fragment size. Radiolabeled probes used to hybridize with DNA fragments will be selected from (a) a large number of RFLPs previously characterized in the human genome, (b) an increasing number of single copy genes, (c) anonymous non-repetitive DNAs from genomic libraries, (d) a panel of candidate genes which could possibly be related to the inherited defect in cystic fibrosis and (e) chromosomal-specific libraries. These probes and biochemical markers from blood cells and serum will be utilized for segregation analysis in families having multiple affected children. The number of informative families will be enhanced by collaboration with other cystic fibrosis centers, colleagues studying linkage, in addition to the families available in the San Antonio and Houston-Galveston areas. A DNA polymorphism segregation with the cystic fibrosis gene can be identified by linkage analysis utilizing the computer program LIPED. The chromosomal location of the DNA polymorphism and thus the CF locus will then be determined by somatic cell hybrid analysis and in situ hybridization on metaphase and prometaphase chromosomal spreads. Further studies to identify the CF locus will include a search for additional markers to facilitate multipoint linkage studies. Utilization of chromosomal-specific libraries, and chromosomal aneuploids due to deletions, duplications and translocations will aid in identification of candidate probes. It is anticipated that as further techniques are developed for chromososme specific cloning procedures these can be utilized for establishing tigher linkage, in addition to cloning and characterizing the CF gene. Exploitation of recombinant DNA techniques offers a promising means of detecting a genetic marker that will be available for tracking the cystic fibrosis gene in affected families.